Note from Dr. Merle A. Sande - The story of azidothymidine is truly a remarkable one. The drug, developed in the 1960s, was rescued from the back shelf because of its potential anti-reverse transcriptase activity. It was found to be active against human immunodeficiency virus; quickly passed phase I, II, and III trials; and received FDA approval for use in patients with severe AIDS-related complex and AIDS. The drug does work, and although it is unlikely to cure human immunodeficiency virus infection, it clearly prolongs life. Therefore, all infectious disease clinicians should be familiar with its use. Dr. Martin Hirsch has been one of our most influential and productive leaders in the search for an agent that can be used to treat human immunodeficiency virus infection. In this commentary, he gives his recommendations on how and when to use this drug, describes the response that can be expected, and predicts what antiviral chemotherapy for AIDS might be available in the future.